The field of the invention is medical devices and methods for their use. More particularly, the invention relates to a catheter device for ablation or other medical procedures that is configured for magnetic resonance imaging.
Magnetic resonance imaging (“MRI”) is considered to be the leading medical imaging modality for monitoring ablation therapies, such as thermal radio frequency ablation in the heart. MRI is capable of utilizing a variety of pulse sequences to monitor the treated tissues for scar formation, temperature elevation, creation of edema, changes in tissue stiffness, changes in elasticity, and the like. MRI is limited, however, in that the use of a surface coil external to the patient's body is required. Such external surface coils restrict imaging to longer scan times that can take several minutes. Alternatively, shorter scan times on the order of a few seconds can be used, but these scan times result in the production of images having very low, and therefore clinically insufficient, spatial resolution. The reason for these limitations is that MRI surface coils have relatively low signal-to-noise (“SNR”) ratios.
One solution to this problem is to use local coils, which can be placed close to the area of interest. While these coils have a smaller field-of-view, they can possess SNRs which are five to ten times that of surface coils. Thus, imaging with a local coil, to obtain the equivalent spatial resolution from an external surface coil, may be conducted at a much faster pace than with surface coils. One example of such a coil is an endorectal coil, which is used for high-resolution prostate imaging. These local coils, while beneficial for the reasons stated above, are more prone to motion artifacts because when the imaged anatomy is moving, these coils will move with the anatomy, thereby resulting in blurred images.
In the context of vascular imaging, there are additional demands on local coils. First, they must be small enough to be inserted via small access vessels to the desired area of operation. Second, they must be designed so as not to block vessels during introduction or during use. Third, for use in therapy, it is preferred that local coils be introduced together with the ablation devices, or other common interventional devices, and that they do not interfere with the ablation process. Fourth, it would be preferable if they can be rapidly moved from site to site during the therapeutic process.
It would therefore be desirable to provide a catheter device that provides both an ablation, or other medical, device to a target region in addition to a clinically useful local coil for MRI. Such a catheter device would desirably not interfere with blood flow during its delivery or operation. It would be additionally desirable if such a catheter device had a reduced susceptibility to motion and the resulting artifacts therefrom in reconstructed images.